Multi-phase stator device

ABSTRACT

Disclosed is a stator device adapted to be arranged in an electrical machine, where the electrical machine further includes a moving device, where the stator device is a multi-phase stator device, where the phases are arranged side-by-side in a direction perpendicular to direction of motion of the moving device, and where each phase comprises a first stator core section having a set of teeth, a second stator core section having a set of teeth, and a coil, and where the teeth are arranged to protrude towards the moving device; and wherein at least two neighboring phases share a stator core section, so that the first stator core section of a first phase and a second stator core section of a second phase is formed as a single unit.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/496,891, filed on Apr. 18, 2012, which is a national stageapplication of International Application No. PCT/EP2010/063796, filed onSep. 20, 2010, which claims the benefit of U.S. Provisional ApplicationNo. 61/244,281, filed on Sep. 21, 2009, and claims the benefit of DanishApplication No. PA 2009 70119, filed on Sep. 21, 2009. The entirecontents of each of U.S. application Ser. No. 13/496,891, InternationalApplication No. PCT/EP2010/063796, U.S. Provisional Application No.61/244,281, and Danish Application No. PA 2009 70119 are herebyincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention generally relates to electric machines. Moreparticularly, the invention relates to a rotating or linearly movingthree-phase transverse flux machine with a permanent magnet rotor ormover structure. This type of machine could be utilized either as amotor or a generator depending on the area of application. A linearlymoving machine may also be denoted a linear machine, a transversallymoving machine or a translational moving machine.

BACKGROUND OF THE INVENTION

The transverse flux machine (TFM) topology is an example of a modulatedpole machine. It is known to have a number of advantages overconventional machines. The basic design of a single-sided radial fluxstator is characterized by a single, simple phase winding parallel tothe air gap and with a more or less U-shaped yoke section surroundingthe winding and exposing in principal two parallel rows of teeth'sfacing the air gap. The state-of-art multi-phase arrangement ischaracterized by stacking magnetically separated single phase unitsperpendicular to the direction of motion of the rotor or mover. Thephases are then electrically and magnetically shifted by 120 degrees fora three-phase arrangement to smooth the operation and produce a more orless even force or torque independent of the position of the rotor ormover. Note here that the angle referred to is given in electricaldegrees which is equivalent to mechanical degrees divided by the numberof pairs of magnetic poles.

A cylindrical motor uses a concentric stator and rotor, and the motionis then considered as rotational or as an end-less rotation. A linearmachine uses translation motion that is normally not a closed motionpattern but may be a back-and-forward motion along a ‘line’. The linearmachine or driver has a mover instead of a rotor. The magnetic circuitmay be arranged by the same basic magnetic principles in both a rotorand mover, however the geometries will differ.

An example of an efficient rotor or mover arrangement is the use of socalled buried magnets combined with soft magnetic pole sections orpieces to allow the permanent magnet field to flux-concentrate or beflexible in a direction transverse to the motion as e.g. described inthe patent application WO2007/024184 by Jack et al.

WO2007/024184 discloses an electrical, rotary machine, which includes afirst stator core section being substantially circular and including aplurality of teeth, a second stator core section being substantiallycircular and including a plurality of teeth, a coil arranged between thefirst and second circular stator core sections, and a rotor including aplurality of permanent magnets. The first stator core section, thesecond stator core section, the coil and the rotor are encircling acommon geometric axis, and the plurality of teeth of the first statorcore section and the second stator core section are arranged to protrudetowards the rotor. Additionally the teeth of the second stator coresection are circumferentially displaced in relation to the teeth of thefirst stator core section, and the permanent magnets in the rotor areseparated in the circumferential direction from each other by axiallyextending pole sections made from soft magnetic material.

The stacking of the individual stator phase sections is normally basedon a physical magnetic separation in-between the individualphase-sections to reduce the magnetic coupling in-between the phasesthat possibly can have an effect of reducing the effective flux in theair gap during operation.

It is desirable in some applications to provide a machine that is asgeometrically compact as possible to fit in a given limited space and tobe able to have a high volume specific performance e.g. expressed asTorque per Volume [Nm/m³].

A conventional, balanced 120 degree phase shift, three-phase sinusoidalor trapezoidal drive scheme does not fully engage the core magneticallyduring the time cycling of operation, and therefore a significant partof the total stator core volume is constantly inefficiently used.

Thus prior art discloses tuning of a set of three phase units at phaseorders 0°, 120°, and 240°.

It remains a problem to optimize performance numbers or values, such astorque pr. volume and/or torque pr. current.

EP 1005136 discloses a transverse flux machine having combined phases.However, it remains desirable to provide a simpler construction of suchan electrical machine.

SUMMARY

Disclosed is an electrical machine comprising a stator device and amoving device,

wherein the stator device is a multi-phase stator device comprising aplurality of phases arranged side-by-side in a lateral direction,perpendicular to a direction of motion of the moving device, where thestator device comprises a plurality of sets of teeth, each toothprotruding towards the moving device and comprising an interface surfacefacing the moving device, wherein the teeth of each set are distributedalong the direction of motion, wherein the plurality of sets of teethcomprises two peripheral sets and a plurality of inner sets arranged inthe lateral direction between the peripheral sets; where the teeth ofthe inner sets are wider, in the lateral direction, than the teeth ofthe peripheral sets and provide a common magnetic flux path shared bytwo neighboring phases.

In embodiments of the electrical machine, the moving device comprises aplurality of permanent magnets separated from each other in saiddirection of motion by pole sections formed as rectilinear rodselongated in the lateral direction, and the pole sections extendlaterally across all phases of the stator. In particular, the interfacesurfaces of the teeth of the peripheral sets may define a lateralextent, measured in the lateral direction, of an active air gap regionbetween the stator device and the moving device; and the rods mayprovide a magnetic flux path extending across the lateral extent of theactive air gap.

In embodiments of the electrical machine, the teeth of the respectivesets are arranged displaced in the direction of motion relative to theteeth of the other sets.

Each phase of the stator device may be formed by two stator coresections wherein the teeth of a first stator core section of a first oneof two neighboring phases and the corresponding teeth of a second statorcore section of a second one of the two neighboring phases are formed asa common set of teeth providing a common magnetic flux path shared byboth neighboring phases.

Hence, teeth of neighboring phases magnetically function as a common setof teeth that are common to the two neighboring/adjacent phases, andthat are magnetically shared by the two neighboring/adjacent phases. Themoving device and the stator device each have a simple constructioninvolving few parts. The parts of the moving device each have a simplegeometric shape, thus allowing efficient and cost-effectiveconstruction.

The teeth of the first stator core section of the first one of twoneighboring phases may be located at the same positions (along thedirection perpendicular to the direction of motion of the moving device)as the corresponding teeth of the second stator core section of thesecond one of the two neighboring phases, i.e. the teeth of the adjacentstator core sections of the neighboring phases may be aligned with eachother in the direction perpendicular to the direction of motion of themoving device. The first stator core section of a first phase and asecond stator core section of a second phase may be formed as twoseparate units arranged back-to-back, e.g. abutting each other, or theymay be formed as a single unit, thus forming a common stator coresection common to the neighboring phases.

Consequently, it is an advantage that the phases are combined tomagnetically share a stator core section during operation, since thisprovides that a significant part of the total stator core volume isconstantly efficiently used.

It is an advantage that the duty cycle of magnetization is improved,since flux paths are shared between the neighboring phases.

It is an advantage that the stator device may function as a single sidedtransverse flux machine, since hereby the volume and weight specificperformance is improved. Thus the performance numbers for e.g. torquepr. volume and/or torque pr. current may be improved.

It is an advantage that the geometrical width of the machine in adirection perpendicular to the direction of motion may be reduced, sincea magnetic separation section in-between the phases results in a largergeometrical width.

Furthermore, it is an advantage that an electrical, rotary machine maycomprise permanent magnets with axially shorter total length than in aconventional stator device with separated phases. It is a furtheradvantage that the axially shorter permanent magnets will result inlower cost.

When the common stator section of neighboring phases is formed as asingle unit, a reduced number of components is required for the statordevice, since a stator core section is shared between two or morephases. In prior art stator devices, each phase has its own separate setof stator core sections.

Furthermore, it is an advantage that there is a higher level ofintegration of the components, since hereby the stator device may bemore robust and may be easier to manufacture.

A set of teeth is defined as a group of teeth, such as a plurality ofteeth.

Since the phases are arranged side-by-side in a direction perpendicularto the direction of motion of the moving device, the direction will beaxial in a rotary machine.

A moving device may be a rotor in a rotationally moving device or amover in a linearly moving device.

In some embodiments the stator core section is a soft magneticstructure. It is an advantage that the improved utilization of softmagnetic structure causes improved performance per volume. In oneembodiment the stator core sections are made of soft magnetic powder. Bymaking the stator core sections from soft magnetic powder themanufacturing of the stator device may be simplified and magnetic fluxconcentration, utilizing the advantage of effective three dimensionalflux paths, may be more efficient.

Each stator core section may comprise a stator core back section and aset of teeth extending from the stator core section, wherein the statorcore back section connects the teeth and provides a flux path betweenneighboring teeth in the direction of motion. A stator core section mayfurther comprise a yoke section that provides a flux path in the lateraldirection towards another stator core section comprising another one ofthe sets of teeth of the same phase.

In some embodiments, the stator device comprises a single yoke sectionconnecting the stator cores sections of all phases. In a rotary machine,the flux bridge may be a stator yoke section arranged concentricallywith the first and second stator core sections. By arranging such astator core section the manufacturing process of the parts of the statorassembly and the assembling process of the stator assembly may befacilitated and more cost-effective.

The stator core section may thus be manufactured so as to only comprisea small number of parts, and allow each tooth of one set of teeth tomagnetically communicate with more than one teeth of another one of thesets of teeth of the same phase.

In some embodiments the stator device is a three-phase stator. An oddnumber of phases is advantageous, because the instantaneous sum of thecurrents is zero that means that the number of supply wires to themachine is reduced by one, and the number of switching devices requiredin the converter is reduced by two. The minimum number of multiple andodd numbered phases is therefore three. Other odd numbers of phases,such as five, seven, nine etc. phases may also be provided. Hence,generally, a multiphase stator device may comprise n phases (n being aninteger and n>1), including two peripheral phases each having a singleneighboring phase and n−2 inner phases, each inner phase having twoneighboring phases, wherein each inner phase comprises two common setsof teeth, each common set of teeth being common/shared with one of therespective neighboring phases of the inner phase, wherein eachperipheral phase comprises a set of peripheral teeth and a set of commonteeth common/shared with the respective neighboring phase of theperipheral phase,

Furthermore, an even number of phases may also be provided, but may notbe as advantageous as an odd number of phases, as described above.

In some embodiments the electric machine is a rotary machine. The movingdevice is a rotor. In this case, the first stator core section, thesecond stator core section, the coil and the rotor may encircle a commongeometric axis. In a rotary machine the lateral direct is an axialdirection of the machine, and the direction of motion is acircumferential direction of the machine.

The permanent magnets in the moving device may be separated in thedirection of motion from each other by laterally extending pole sectionsin the form of rectilinear rods. The pole sections may be made of a softmagnetic powder. The permanent magnets may be magnetized in thedirection of motion and with alternating orientation. Generally, thepermanent magnets may also be rectilinear rods elongated in the lateraldirection; the rods may extend across the lateral extent of the activeair gap

In some embodiments the electrical machine is a modulated pole machinesuch as a transversal flux machine.

In conventional machines, the coils explicitly form the multi-polestructure of the magnetic field, and the magnetic core function is justto carry this multi-pole field to link the magnet and/or other coils.

In a modulated pole machine, it is the magnetic circuit which forms themulti-pole magnetic field from a much lower, usually two, pole fieldproduced by the coil. In a modulated pole machine, the magnets usuallyform the matching multi-pole field explicitly but it is possible to havethe magnetic circuit forming multi-pole fields from a single magnet.

The modulated pole machine has a three-dimensional (3D) flux pathutilizing magnetic flux paths in the transverse direction both in thestator and in the moving device, e.g. in the axial direction in arotating machine, where the moving device is a rotor. The 3-dimensionalflux paths are particularly suitable when utilizing the combined phasesstator.

Thus in some embodiments the stator device and/or the moving devicecomprise a three-dimensional (3D) flux path including a flux pathcomponent in the transverse direction relative to the direction ofmovement.

The benefit of having the modulation is that every pole sees all of themagneto motive force (MMF) of the coil, so that as the pole numberrises, the magnetic field strength (MMF/meter) rises with it without anychange in the coil. This may be compared with a conventional machine inwhich as the pole number rises, so does the number of coils and hencethe smaller each coil is. The pole pitch however also falls with polenumber, so that as the pole number rises, the magnetic field strength ismore or less constant in a conventional machine as the MMF/coilreduction balances with the reduction in pole pitch.

The natural design for a modulated pole machine is for a high polenumber. This may make very high electric loading, i.e. magnetic fieldstrength, possible with modest requirements for the volume of theconductor required.

Thus a modulated pole machine will show its largest advantage incircumstances where the pole number is high and the possible electricloading using conventional coils is low.

In some embodiments the modulated pole machine comprises a claw polearrangement or extension.

For modulated pole machines, taking as fixed a geometry which formstorque from a circumferential/axial surface i.e. a radial field machine,the field may be carried radially across the air gap with the magneticcircuit, circumferentially by one pole pitch, which can be done in thestator or the rotor or partially in both, and axially in both directionsto enclose the coil. If the axial circuit is closed in the stator aroundthe coil, the claw pole arrangement is produced.

A claw pole arrangement or extension may be used together with thecombined phases, but the axial claw extension should be limited or smallin order not to cause leakage. Leakage may occur when the claws overlapeach other, since these overlapping faces may provide an unwanted pathfor leakage flux. Even if claws only stretch to half the phase axialwidth, they may come in close proximity and that may cause a lot ofunwanted magnetic leakage, so only small or minor claws should be usedwhen using combined phases. Thus it is possible to use minor claws,defined as semi-claw poles, to adjust the pole tip area but the clawsmay not be able to overlap axially since the phase shift of the combinedphases hinders the free extension of claws across the stators axialextension.

The present invention relates to different aspects including the statordevice described above and in the following, and corresponding methods,devices, and/or product means, each yielding one or more of the benefitsand advantages described in connection with the first mentioned aspect,and each having one or more embodiments corresponding to the embodimentsdescribed in connection with the first mentioned aspect and/or disclosedin the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional objects, features and advantages of thepresent invention, will be further elucidated by the followingillustrative and non-limiting detailed description of embodiments of thepresent invention, with reference to the appended drawings, wherein:

FIGS. 1 a-1 d show examples of a prior art machine and stator devicewith separated phases.

FIG. 2 shows an example of a cross-section of three-phase machine withseparate phases.

FIG. 3 shows an example of a magnetic flux phasor diagram of athree-phase machine with separate phases

FIG. 4 shows an example of a stator arrangement of a three-phase machinewith separate phases showing a stator from the normal direction of theair gap plane.

FIG. 5 shows an example of a stator device with magnetically combinedphases.

FIG. 6 shows an example of a cross-section of a three-phase machine withmagnetically combined phases.

FIG. 7 shows an example of a magnetic flux phasor diagram of athree-phase machine with magnetically combined phases.

FIG. 8 shows an example of a stator arrangement of a three-phase machinewith magnetically combined phases showing a stator from the normaldirection of the air gap plane.

FIG. 9 shows an example of the structure of a three-phase machine withmagnetically combined phases.

FIGS. 10 a and 10 b show examples of the structure of a three-phaselinearly moving machine.

FIGS. 11 a and 11 b show examples of the structure of three-phasemachines with magnetically combined phases and semi-claw poles.

FIG. 12 shows an example of flux paths in the stator device and in themoving device.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingfigures, which show by way of illustration how the invention may bepracticed.

FIGS. 1 a-4 show examples of a three-phase machine with separate phases,which may be termed a Separate Phase Modulated Pole Machine (SPMPM).

FIGS. 1 a)-1 b) show an example of a prior art three-phase radialmachine. An electrical, rotary machine comprises a stator assembly and arotor. For the purpose of the present description, primed referencenumerals with ′ generally refer to a feature of a first phase, ″ to acorresponding feature of a second phase and ′″ to a correspondingfeature of a third phase, while reference numerals without prime referto the corresponding features of all phases. Three stator assemblies10′, 10″, 10′″ are shown, and each stator assembly comprises a firststator core section 14, a second stator core section 16, a stator yokesection 18 and a coil 20. Three rotors 12′, 12″, 12′″ are shown, andeach rotor 12 comprises permanent magnets 22 and pole sections 24. Anaxle 50 onto which the rotor is mounted is shown. Each stator coresection 14, 16 is essentially circular in shape and includes a pluralityof radially extending teeth 26. The teeth are arranged to extend towardsthe rotor 12 for forming a closed circuit flux path with the rotor 12.

Each of the phase sections, i.e. single phase machines, is shownincluding a rotor of its own, i.e. each phase section correspondscompletely to a single phase machine.

FIG. 1 c) shows an example of spatial separation between phasesaccording to prior art. In the figure the first stator core section 14′,14″, 14′″ of each phase is shown. The spatial separation in this examplerelates to the teeth 26 of the stator core section of one phase beingcircumferentially displaced in relation to the teeth of the stator coresection of the other phases

The schematic example of a stator device with separated phases in FIG. 1d) shows three separated phases, phase 1 of stator assembly 10′, phase 2of stator assembly 10″, and phase 3 of stator assembly 10′″.

Each basic unit or phase unit comprises a single coil or core 20, afirst stator core section 14, a second stator core section 16, and astator yoke section 18. This phase unit creates a unidirectional butpulsing torque.

FIG. 2 shows a cross-section of a three-phase Separate Phase ModulatedPole Machine (SPMPM). Phase 1 is indicated by A, stator core section 14′and stator assembly 10′, phase 2 is indicated by B, stator core section14″ and stator assembly 10″, and phase 3 is indicated by C, stator coresection 14′″ and stator assembly 10′″. The first stator core section 14,the second stator core section 16, and the stator yoke section 18 isshown for each phase unit.

The rotor 12 is seen, and the air gap 30 between the rotor and each ofthe stator assemblies, 10′, 10″, 10′″, is seen. The magnetic flux, ψ,path for each of the phases are seen, ψ_(A) for phase A, ψ_(B) for phaseB, and ψ_(C) for phase C. The value of the separate fluxes, + or −, atthe air gap 30 is also shown.

FIG. 3 shows a magnetic flux phasor diagram for the separated phaseunits. The displacement of the phase units is 120°. The magnetic flux ofphase 1 is indicated by ψ_(A), the magnetic flux of phase 2 is indicatedby ψ_(B), and the magnetic flux of phase 3 is indicated by ψ_(C).

FIG. 4 shows an example of the displacement of phase units, phase A,phase B and phase C relative to the rotor pole. The rotor pole referenceis indicated by the dotted rectangle 121 across phase A, phase B andphase C. The teeth 26 and the coils 20 of the phase units are shown. Theteeth 26 are part of the stator core sections, as seen in FIG. 1 b). Thedisplacements of 120° between the phase units are seen and indicated bythe position of the numbers 0°, 120°, 240° and 360°.

Each of these phase units has two sets of armature teeth 26, as seen inFIG. 1 b), where the first stator core section 14 includes one set ofteeth and the second stator core section 16 includes the other set ofteeth. One set emanates from the left side of the coil 20 and has anorth pole when driven with a certain direction of armature current, theother set emanates from the right side of the coil 20 and has a southpole when driven by the same direction of current.

When multiple phase units are used they are separated from each otheraxially, and this means that the teeth on the right side of the leftmostunit are in close proximity with the teeth of the left side of the nextphase unit and so on for each of the units with facing sides.

However, this close proximity is not beneficial for the most obviouschoices of angle displacement of the teeth.

FIGS. 5-9 show examples of a three-phase machine with combined phases,which may be termed the Combined Phase Modulated Pole Machine (CPMPM).

The combined phase machine comprises a stator assembly 10 as seen inFIG. 5 and FIG. 6, and a moving device 12, e.g. a rotor, as seen in FIG.6. In FIGS. 5, 6 and 8, the reference numerals with ′ refers to afeature of a first phase, ″ to a feature of a second phase and ′″ to afeature of a third phase.

FIG. 5 shows that the stator assembly 10 comprises three phases, phase1, phase 2 and phase 3. Phase 1 and phase 3 may be designated asperipheral phases and phase 2 may be designated an inner phase. Eachphase comprises a single coil or core 20, which may be supplied withdifferent voltages for operation, e.g. sinusoidal or square wave. Eachphase furthermore comprises a first stator core section 14, and a secondstator core section 16. As is seen in the figure, the first stator coresection 14″ of phase 2 and the second stator core section 16′ of phase 1are formed as a single unit. Similarly, the first stator core section14′″ of phase 3 and the second stator core section 16″ of phase 2 areformed as a single unit. Furthermore, the first stator core section 14′of phase 1 is a single unit that is not shared with any other phase, andlikewise the second stator core section 16′″ of phase 3 is a singleunit. Thus there are four single units, where two of the single unitseach are shared between two different phases.

The stator assembly 10 comprises a stator yoke section 18, which iscommon for and shared by all the phases. The stator yoke section isarranged to provide a magnetic flux path between stator core sections,thereby acting as a flux bridge. The material used for the stator yokesection may be soft magnetic powder in order to facilitate the assemblyof the stator and to provide a relatively low reluctance transitionbetween a first and a second stator core section.

A moving device is not shown in FIG. 5, but a moving device would beconfigured to be arranged at the top of the figure, so that the movingdevice is close to the coils 20.

FIG. 6 shows a cross-section of the three-phase Combined Phase ModulatedPole Machine (CPMPM). The stator assembly 10 comprises phase 1 indicatedby A, phase 2 indicated by B, and phase 3 indicated by C. The firststator core section 14 and the second stator core section 16 are shownfor each phase unit. The stator yoke section 18 is shared by and commonfor the three phases.

A moving device 12, which may be a rotor or mover, is shown, and themoving device comprises sections of permanent magnets and pole sections(not shown), which may be made from soft magnetic material. The polesections are arranged between the permanent magnets, thereby separatingthe permanent magnets from each other. More about pole sections,permanent magnets and flux is described in WO2007/024184.

If the moving device 12 is a rotor, the rotor 12 may be arranged on anaxle or shaft (not shown), and positioned in the center of the statorassembly 10 or, if the rotor is an outer rotor type, around the statorassembly. If the moving device 12 is a mover, the device may be a flat,linear device which does not have any inside or outside as the rotor,instead the mover moves just up and down or right or left.

An air gap 30 between the common stator assembly 10 and the movingdevice 12 is also shown in FIG. 6.

The moving device 12, e.g. the rotor, is arranged for interaction withall three phase sections, i.e. the rotor may extend in the axialdirection in order to interact with all three phase sections. Theelectrical machine may comprise radial phase sections or axial phasesections or a combination.

Each of the stator core sections, 14′, 16′, 14″, 16″, 14′″ and 16′″, maybe essentially circular in shape and include a plurality of radiallyextending teeth as seen in FIG. 8. The teeth are arranged to extendtowards the moving device 12, e.g. the rotor, for forming a closedcircuit flux path with the rotor 12. The teeth may extend inwardstowards an inner rotor, or the rotor may be arranged outside the statorcore sections, 14, 16, whereby the teeth should be arranged to extendradially outwards instead.

The magnetic flux ψ path for each of the phases are seen, ψ_(A) forphase A, ψ_(B) for phase B, and ψ_(C) for phase C. The values of thecombined fluxes at the air gap 30 are also shown.

The first 14 and second 16 stator core sections may be axially displacedin relation to each other and they may be arranged around a common axis.Each coil 20 may be arranged between the first 14 and the second 16stator core section. The advantage of arranging the coil 20 like this isthat all of the MMF (Magneto Motive Force) is seen by every pole and,thus, results in high electric loading and high output for given sizeand/or cost. The stator yoke section 18 may be arranged concentricallyto the first 14 and the second 16 stator core sections. The stator yokesection 18 may be substantially of a width, in the axial direction,corresponding to the width of the assembly of the first 14 and thesecond 16 stator core sections and the coil 20, in order to be arrangedas a flux bridge between the first 14 and the second 16 stator coresection. By making the stator yoke section 18 from soft magnetic powder,the efficiency of the three dimensional flux path going from the first14 and the second 16 stator core sections to the stator yoke section 18is increased in relation to an embodiment where the stator yoke sectionis made from laminates. Further, one of the first 14 and the second 16stator core sections may be rotationally displaced in relation to theother of the first 14 and the second 16 stator core section. Thisdisplacement results in that the teeth, see FIG. 8, of one of the first14 and the second 16 stator core sections are positioned at acircumferential position different from the circumferential position ofthe teeth of the other of the first 14 or the second 16 stator coresection. Each tooth of one of the first 14 or the second 16 stator coresections may be positioned, in the circumferential direction, in themiddle of the gap between two teeth of the other of the first 14 or thesecond 16 stator core section.

The concept of displacing the teeth of one of the first 14 or the second16 stator core section in relation to the teeth of the other stator coresection is advantageous in order to make effective use of the abovedescribed and most effective design of the moving device.

FIG. 8 shows the displacement of the combined phase units, phase A,phase B and phase C relative to the moving device pole, e.g. the rotorpole. The rotor pole reference 121 is indicated by the dotted rectangleacross phase A, phase B and phase C. The coil 20 of each of the phaseunits is shown. Each phase, A, B, C, comprises a first stator coresection (not shown), and a second stator core section (not shown), andthe stator core sections comprise teeth. As was seen in FIG. 5, thefirst stator core section 14″ of phase 2, which corresponds to phase Bhere, and the second stator core section 16′ of phase 1, whichcorresponds to phase A here, are formed as a single unit. Thus the teeth27 are shared by phase A and B. Similarly, the first stator core section14′″ of phase 3, which corresponds to phase C here, and the secondstator core section 16″ of phase 2, corresponding to phase B here, areformed as a single unit, and therefore the teeth 28 are shared by phaseB and C. Furthermore, the first stator core section 14′ of phase 1,corresponding to phase A here, is a single unit, and the teeth 26′ arenot shared by two phases. Likewise the second stator core section 16′″of phase 3, corresponding to phase C here, is a single unit, and theteeth 26′″ are not shared by two phases. Thus there are four singleunits, where two of the single units each are shared by two differentphases, whereby each of the set of teeth 27 and 28 are shared by twodifferent phases.

The displacements between the phases are seen and indicated by theposition of the numbers 0°, 150°, 270°, and 60°, respectively, which aredescribed in more detail below.

Thus one single set of teeth may be used to share sequential phasesinstead of using separate phase units. The selection of the appropriateorientation of each set of teeth can provide a significant benefit. Iffor example, a three phase machine with three coils arranged axially isprovided, this gives four sets of teeth, one at either end, and one setbetween phases 1 and 2 and another set between phases 2 and 3, see FIG.8. The choice of angle is not intuitive, but should be close to 0°,150°, 270° and 60° for each of the four teeth sets taken from one end tothe other.

According to some embodiments, the middle sets of teeth have a differentaxial width than the sets of teeth at the ends, as seen in FIG. 8, whichprovide a slight adjustment in axial width to make a truly balanced setof flux linkages and torques between the three phases.

An example of the structure of a three-phase rotating machine withcombined phases is shown in FIG. 9.

FIG. 9 shows a stator device 10 and a moving device 12 in the form of arotor. The reference numerals with ′ refer to a feature of a firstphase, ″ to a feature of a second phase and ′″ to a feature of a thirdphase. The stator device 10 comprises three phases, where each phasecomprises a coil 20, a first stator core section 14 and a second statorcore section 16. One rotor 12 is shown which encloses the stator device10. The rotor 12 comprises permanent magnets 22 and pole sections 24extending along the entire stator device 10. An axle onto which thestator is mounted may be provided (not shown). Each stator core section14, 16 is essentially circular in shape and includes a stator core backsection 29 and a plurality of radially extending teeth which extend fromthe stator core back section. The teeth are arranged to extend outwardstowards the rotor 12 for forming a closed circuit flux path with therotor 12. The stator core back section 29 connects the teeth in thecircumferential direction. The stator cores sections further comprise ayoke section 23 extending axially from the stator core back section 29towards the neighboring stator core section so as to provide an axialflux bridge.

The second stator core section 16′ of phase 1 and the first stator coresection 14″ of phase 2 are arranged as one unit, i.e. a combined statorcore section, whereby phase 1 and phase 2 share a stator core section.Thus the teeth 27 of the combined phase unit are arranged to be sharedbetween phase 1 and phase 2, whereby the set of teeth of the firststator section 14″ of phase 2 and the set of teeth of the second statorcore section 16′ of phase 1 are formed as one unit.

The teeth 28 of the combined phase unit are arranged to be sharedbetween phase 2 and phase 3, whereby the set of teeth of the firststator section 14′″ of phase 3 and the set of teeth of the second statorcore section 16″ of phase 2 are formed as one unit.

The teeth 26 at each end of the stator device 10 are not shared betweentwo phases, and thus the teeth 26′ belong only to phase 1 and the teeth26′″ belongs only to phase 3. Furthermore, the teeth 26′ and 26′″ of theperipheral phases 1 and 3 define the axial extent of the active air gapregion of the stator which axially extends between the peripheral edgesof the teeth 26′ and 26″, respectively. The permanent magnets 22 andpole sections 24 extend axially across the entire active air gap region,i.e. between the axially outer edges of the surfaces of teeth 26′ and26′″ facing the rotor.

An example of the structure of a three-phase linearly moving machinewith combined phases is shown in FIG. 10 a). FIG. 10 b) shows a linearlymoving machine FIG. 10 a) shows a stator device 10 and a moving device12 in the form of a mover adapted to move linearly or transversallyalong the stator device. The reference numerals with ′ refer to afeature of a first phase, ″ to a feature of a second phase and ′″ to afeature of a third phase. The stator device 10 comprises three phases,where each phase comprises a coil 20, a first stator core section 14 anda second stator core section 16. The mover 12 comprises permanentmagnets 22 and pole sections 24 extending along the entire stator device10. Each stator core section 14, 16 is essentially linear in shape andincludes a plurality of linearly extending teeth. The teeth are arrangedto extend towards the mover 12 for forming a closed circuit flux pathwith the mover 12.

The second stator core section 16′ of phase 1 and the first stator coresection 14″ of phase 2 are arranged as one unit, i.e. a combined statorcore section, whereby phase 1 and phase 2 share a stator core section.Thus the teeth 27 of the combined phase unit are arranged to be sharedbetween phase 1 and phase 2, whereby the set of teeth of the firststator section 14″ of phase 2 and the set of teeth of the second statorcore section 16′ of phase 1 are formed as one unit.

The teeth 28 of the combined phase unit are arranged to be sharedbetween phase 2 and phase 3, whereby the set of teeth of the firststator section 14′″ of phase 3 and the set of teeth of the second statorcore section 16″ of phase 2 are formed as one unit.

The sets of teeth 26 at each of the two ends of the stator device 10 arenot shared between two phases, and thus the teeth 26′ belong only tophase 1 and the teeth 26′″ belongs only to phase 3.

In FIG. 10 b) all the three phases are separated, and thus first 14 andsecond 16 stator core sections are not shared between any phases. Thusthere are only sets of separate teeth 26, i.e. teeth belonging to onlyone phase, in the machine of FIG. 10 b).

Examples of the structure of three-phase machines with combined phasesand semi-claw poles are shown in FIGS. 11 a and 11 b.

FIGS. 11 a) and 11 b) show a stator device 10 and a moving device 12. InFIG. 11 a) the moving device 12 is a rotor, which is shown enclosing thestator device 10, and in FIG. 11 b) the moving device 12 is a moveradapted to move linearly or transversally along the stator device. Thereference numerals with ′ refer to a feature of a first phase, ″ to afeature of a second phase and ′″ to a feature of a third phase. Thestator device 10 comprises three phases, where each phase comprises acoil 20, a first stator core section 14 and a second stator core section16. The moving device 12 comprises permanent magnets 22 and polesections 24 extending along the entire stator device 10. Each statorcore section 14, 16 includes a plurality of extending teeth. The teethare arranged to extend towards the moving device 12 for forming a closedcircuit flux path with the moving device 12. The second stator coresection 16′ of phase 1 and the first stator core section 14″ of phase 2are arranged as one unit, i.e. a combined stator core section, wherebyphase 1 and phase 2 share a stator core section. Thus the teeth 27 ofthe combined phase unit are arranged to be shared between phase 1 andphase 2, whereby the set of teeth of the first stator section 14″ ofphase 2 and the set of teeth of the second stator core section 16′ ofphase 1 are formed as one unit.

The set of teeth 28 of the combined phase unit are arranged to be sharedbetween phase 2 and phase 3, whereby the set of teeth of the firststator core section 14′″ of phase 3 and the set of teeth of the secondstator core section 16″ of phase 2 are formed as one unit. The set ofteeth 26 at each end of the stator device 10 are not shared between twophases, and thus the set of teeth 26′ belongs only to phase 1 and theteeth 26′″ belongs only to phase 3.

Furthermore, the combined phases machines of FIGS. 11 a) and 11 b)comprise semi-claw poles 40, which are short extensions of the teeth inthe set of teeth 26′, 27, 28 and 26′″ that overlap the coils 20. Thesemi-claw poles are short, small or minor claw poles, i.e. claw poleswhich do not extend along the entire axial width of a phase, but whichonly extend along a small part of the axial width, whereby magneticleakage is avoided or reduced. FIGS. 11 a) and 11 b) show that thesemi-claw poles 40 are arranged integrated with the teeth. The sets ofteeth 27 and 28 which are each shared between two phases comprise thesemi-claw poles in both ends of the teeth, i.e. adjacent to coils 20,whereas the sets of teeth 26′ and 26′″, which are not shared between twophases but only belongs to one phase, only comprise the semi-claw polesin the end of the teeth adjacent to the respective coils 20′ and 20′″.

An improvement of 30% in torque compared to prior art machines can berealized, when using the same magnets, same stator magneto motive force,same bore and same air gap width.

A larger and smoother torque can be created when employing multiplephase units which are mechanically and electrically displaced in angularposition, instead of employing only one phase. For instance, a threephase machine can have the phase units mechanically displaced by ⅓^(rd)of the pitch of a pair of poles, or 120 degrees electrical angle and thephase currents separated by the same angle in time, while using a singlemoving device structure, e.g. a rotor structure, extending through oraround the three stators.

A similar effect can be gained using three stator units all aligned incircumferential position but supplied with currents which are 120 degreein time apart to act in combination with three moving device sections,e.g. rotor sections, one for each phase which are displaced 120 degreesapart circumferentially.

As mentioned, a prior art Separate three-Phase Modulated Pole Machinehas three phases with a 120° displacement between each phase as seen inFIG. 3. Each phase consists of two sets of teeth, displaced by 180°,forming a set of north poles and a set of south poles. The three phasemachine consists of six sets of teeth (in three pairs) plus three coils.Each phase is separated from the adjacent phase by a small distance orair gap, see FIG. 2, to ensure minimal magnetic coupling between phases.

When the phase are combined instead of being separated, as seen in FIGS.5, 6 and 8, adjacent teeth now have a shared flux path, as seen in FIG.6. Merging adjacent teeth may result in a machine with four sets ofteeth and three coils, see FIG. 8, and with a common moving device, e.g.rotor, stretching the full axial width of the machine.

Each set of teeth should be positioned at a certain angle, and gather acertain amount of flux to ensure a balanced three phase operation, whereeach coil links flux of an equal magnitude and at a phase angle of 0°,120° and 240° respectively, see FIG. 7.

To calculate the conditions for which a balanced three phase set of coilfluxes result, the Combined Phase Modulated Pole Machine is analyzedwith the following assumptions:

-   -   the air gap flux density is constant in the axial direction and        varies sinusoidally in the circumferential direction;

flux entering a tooth, ψ=ba, where b is the air gap flux density and ais the air gap surface area of the tooth;

-   -   the angular position of the tooth (circumferentially) determines        the phase angle of the flux entering the tooth;    -   the flux traversing in the axial direction through the coreback        directly over a coil is equal to the flux linking the coil.

In the following, reference is made to the phasor diagrams in FIGS. 3and 7.

A balanced three phase machine has the following coil flux linkages:ψA=|ψ|<0°ψB=|ψ|<120°ψC=|ψ|<240°

The teeth are numbered 1, 2, 3, 4 in the axial direction, summing theflux entering each tooth:ψ1=ψAψ2=ψB−ψAψ3=ψC−ψBψ4=−ψC

Relating the tooth flux to the required balanced three coil fluxes, asshown in the phasor diagram in FIG. 7, results in the following toothfluxes:ψ1=|ψ|<0°ψ2=|√3ψ|<150°ψ3=|√3ψ|<270°ψ4=|ψ|<60°

Therefore for a balanced three phase machine, the teeth (1, 2, 3, 4) maybe positioned at a phase angle of 0°, 150°, 270°, 60°, where a phaseangle of 360° corresponds to the circumferential pitch distance betweenneighboring teeth, Hence, the angular displacement of the teeth relativeto one of the sets of teeth is 0°/N, 150°/N, 270°/N, 60°/N, where N isthe number of teeth in each set of teeth. Furthermore, a correct surfacearea may be ensured when the relative axial widths of the teeth in therespective sets of teeth are: 1, √3, √3 and 1, respectively. Hence, theinner teeth that are shared between two neighboring phases are wider bya factor of √3 than the peripheral teeth that are not shared betweenphases but only belong to a single phase.

FIG. 7 shows a magnetic flux phasor diagram for the combined phases,where the angles are shown, as well as the axial width of 1 unit, √3units, √3 units and 1 unit, respectively. The magnetic fluxes of thecombined phases are also seen.

FIG. 12 shows an example of flux paths in the stator device and in themoving device. The modulated pole machine has a three-dimensional (3D)flux path utilizing magnetic flux paths in the ‘axial’ transversedirection both in the stator and in the moving device, e.g. rotor.

In FIG. 12 a moving device 12, e.g. a rotor, is seen from radial outwardposition relative to the stator device 10 of which three teeth 26 areoutlined. The axial 304 and tangential 305 directions of the movingdevice/stator device are depicted. A number of the permanent magnets 22in the moving device are shown as hatched areas with the pole sections24 in between. In the sketch the stator teeth 26 are in the situation ofbeing just opposite a pole section 24 yielding the main magnetic fluxpath 300 as shown by the thick lines. As can be seen the flux directionthrough the permanent magnets 22 are primarily 2-dimensional whereas theflux through the pole sections 24 is 3-dimensional. Furthermore, themagnetic flux is concentrated primarily in the central regions 301 ofeach permanent magnet 22 between two neighboring pole sections. Thisdesign of the moving device 12 thus enables flux concentration from thepermanent magnets so that the surface of the moving device 12 facing astator tooth 26 may present the total magnetic flux from both of theneighboring permanent magnets to the surface of the tooth. The fluxconcentration may be seen as a function of the area of the permanentmagnets facing each pole section divided by the area facing a tooth.These flux concentration properties of each pole section makes itpossible to use weak low cost permanent magnets as permanent magnets inthe moving device and makes it possible to achieve very high air gapflux densities. The flux concentration may be facilitated by the polesection being made from soft magnetic powder enabling effective threedimensional flux paths as illustrated.

Even though not shown in FIG. 12, there is a corresponding 3-dimensionalflux path in the stator device.

As also seen in FIG. 8, the 3-dimensional flux path comprises the axialor transverse flux path of the moving device 12, where the flux path istransverse to the motion direction. The 3-dimensional flux paths in thestator device and in the moving device are particularly suitable whenutilizing the combined phases stator.

Both a radial machine or an axial machine or a mix of axial and radialare possible.

In case of the axial flux version, the teeth areas which are facing theair gap may form concentric rows with the coils or windings in betweenthese rows. So a three-phase version can be designed with three separatesets each of two concentric rows of teeth and a coil or winding with adistance to the nearest phase set to avoid magnetic coupling. Thus theaxial, combined phase arrangement may combine two neighboring oradjacent rows of teeth in the same way as for the radial air gap fluxversion (see e.g. FIG. 8).

Generally, the stator structures described herein may be made of a softmagnetic powder, e.g. a substantially pure water atomized iron powder ora sponge iron powder having irregular shaped particles which have beencoated with an electrical insulation. In this context the term“substantially pure” means that the powder should be substantially freefrom inclusions and that the amount of the impurities O, C and N shouldbe kept at a minimum. The average particle sizes are generally below 300μm and above 10 μm.

However, any soft magnetic metal powder or metal alloy powder may beused as long as the soft magnetic properties are sufficient and thepowder is suitable for die compaction.

The electrical insulation of the powder particles may be made of aninorganic material. Especially suitable are the type of insulationdisclosed in U.S. Pat. No. 6,348,265 (which is hereby incorporated byreference), which concerns particles of a base powder consisting ofessentially pure iron having an insulating oxygen- andphosphorus-containing barrier. Powders having insulated particles areavailable as Somaloy®500, Somaloy®550 or Somaloy®700 available fromHöganäs AB, Sweden.

Although some embodiments have been described and shown in detail, theinvention is not restricted to them, but may also be embodied in otherways within the scope of the subject matter defined in the followingclaims. In particular, it is to be understood that other embodiments maybe utilized and structural and functional modifications may be madewithout departing from the scope of the present invention.

In device claims enumerating several means, several of these means canbe embodied by one and the same item of hardware. The mere fact thatcertain measures are recited in mutually different dependent claims ordescribed in different embodiments does not indicate that a combinationof these measures cannot be used to advantage.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

The invention claimed is:
 1. An electrical machine comprising a statordevice and a moving device, wherein the stator device is a multi-phasestator device comprising a plurality of phases arranged side-by-side ina lateral direction, perpendicular to a direction of motion of themoving device, where the stator device comprises a plurality of sets ofteeth, each tooth protruding towards the moving device and comprising aninterface surface facing the moving device, wherein the teeth of eachset are distributed along the direction of motion, wherein the pluralityof sets of teeth comprises two peripheral sets and a plurality of innersets arranged in the lateral direction between the peripheral sets;where the teeth of the inner sets are wider, in the lateral direction,than the teeth of the peripheral sets and provide a common magnetic fluxpath shared by two neighbouring phases; wherein the interface surfacesof the teeth of the peripheral sets define a lateral extent of an activeair gap region between the stator device and the moving device; whereinthe stator device comprises at least two separate stator core sectionsthat abut each other and share one of the plurality of phases; whereinthe moving device comprises a plurality of permanent magnets separatedfrom each other in said direction of motion by pole sections formed asrectilinear rods elongated in the lateral direction, the rods providinga magnetic flux path extending across the lateral extent of the activeair gap region; and wherein the teeth of the respective sets arearranged displaced in the direction of motion relative to the teeth ofthe other sets.
 2. The electrical machine according to claim 1, whereinthe stator device comprises a plurality of stator core sections, eachstator core section comprising one of the sets of teeth.
 3. Theelectrical machine according to claim 2, wherein the stator devicecomprises a plurality of windings arranged between respective statorcore sections.
 4. The electrical machine according to claim 2, whereineach stator core section comprises a stator core back section and a setof teeth extending from the stator core section, wherein the stator coreback section connects the teeth and provides a flux path betweenneighboring teeth in the direction of motion.
 5. The electrical machineaccording to claim 4, wherein each stator core section further comprisesa yoke section that provides a flux path in the lateral directiontowards another stator core section comprising another one of the setsof teeth of the same phase.
 6. The electrical machine according to claim1, wherein the stator core sections are made from soft magnetic powder.7. The electrical machine according to claim 1, comprising a number n ofphases, including two peripheral phases each having a singleneighbouring phase, and n−2 inner phases each having two neighbouringphases; wherein each inner phase comprises two common sets of teeth,each common set of teeth being magnetically shared with one of therespective neighbouring phases of the inner phase, wherein eachperipheral phase comprises a set of peripheral teeth and a set of commonteeth, the common teeth being magnetically shared with the respectiveneighbouring phase of the peripheral phase, and wherein the common teethhave a width in a direction perpendicular to a direction of motionlarger than the corresponding width of the peripheral teeth and smallerthan twice the corresponding width of the peripheral teeth.
 8. Theelectrical machine according to claim 1, wherein the stator device is athree-phase stator.
 9. The electrical machine according to claim 1,wherein the electrical machine is a rotary machine, and wherein themoving device is a rotor.
 10. The electrical machine according to claim9, wherein the stator device is a three-phase stator and comprises foursets of teeth, each set comprising N teeth, N being an integer numberlarger than 1, and wherein the teeth of the respective sets of teeth arearranged circumferentially displaced at angles 0°/N, 150°/N, 270°N,60°/N relative to the teeth of a first one of the sets of teeth.
 11. Theelectrical machine according to claim 1, wherein the stator devicecomprises four sets of teeth and lateral widths of the four sets ofteeth are 1 unit, √3 units, √3 units, 1 unit, respectively.
 12. Theelectrical machine according to claim 1, wherein the moving device is amover arranged to move linearly in the direction of motion of the movingdevice.
 13. The electrical machine according to claim 1, wherein theelectrical machine is a modulated pole machine.
 14. The electricalmachine according to claim 1, wherein the stator device and/or themoving device provide a three-dimensional (3D) flux path including aflux path component in the transverse direction relative to thedirection of motion.
 15. The electrical machine according to claim 1,wherein each stator core section comprises a stator core back sectionthat is continuous along the direction of motion of the moving device,and a set of teeth extending from the stator core back section.
 16. Astator device adapted to be arranged in an electrical machine, where theelectrical machine further comprises a moving device, where the statordevice is a multi-phase stator device, where the phases are arrangedside-by-side in a direction perpendicular to a direction of motion ofthe moving device, and where each phase comprises two stator coresections each having a respective set of teeth, a flux bridge connectingthe stator core sections, and a coil, and where the teeth are arrangedto protrude towards the moving device; and wherein the teeth of a firststator core section of a first one of two neighbouring phases and thecorresponding teeth of a second stator core section of a second one ofthe two neighbouring phases provide a common magnetic flux path sharedby both neighbouring phases; and wherein the stator device comprises atleast two separate stator core sections that abut each other and shareone of the plurality of phases.
 17. The stator device according to claim16, wherein the teeth of the first stator core section of the first oneof the two neighbouring phases are located at the same positions in thedirection perpendicular to the direction of motion of the moving deviceas the corresponding teeth of the second stator core section of thesecond one of the two neighbouring phases.
 18. The stator deviceaccording to claim 16, wherein each stator core section is a softmagnetic structure.
 19. The stator device according to claim 16, whereinthe sets of teeth of the respective stator core sections of each phaseare arranged displaced with respect to each other in the directionperpendicular to the direction of motion of the moving device by arespective displacement, and wherein at least two of the phases havedifferent displacements.
 20. The stator device according to claim 16,wherein the teeth of each stator core section have a respective width inthe direction perpendicular to the direction of motion of the movingdevice, and where the teeth of a first stator core section have a widthdifferent from a width of the teeth of a second stator core section. 21.A stator device according to claim 16, wherein the first stator coresection and the second stator core section are formed as a single unitcomprising a set of common teeth common to the first and second statorcore sections.
 22. The stator device according to claim 16, comprising anumber n of phases, including two peripheral phases each having a singleneighbouring phase, and n−2 central phases each having two neighbouringphases; wherein each central phase comprises two common sets of teeth,each common set of teeth being magnetically shared with one of therespective neighbouring phases of the central phase, wherein eachperipheral phase comprises a set of peripheral teeth and a set of commonteeth, the common teeth being magnetically shared with the respectiveneighbouring phase of the peripheral phase, and wherein the common teethhave a width in a direction perpendicular to a direction of motionlarger than the corresponding width of the peripheral teeth and smallerthan twice the corresponding width of the peripheral teeth.
 23. Thestator device according to claim 16, wherein the stator device is athree-phase stator.
 24. The stator device according to claim 23, whereinthe stator device comprises four sets of teeth, each set comprising Nteeth, N being an integer number larger than 1, and wherein the teeth ofthe respective sets of teeth are arranged circumferentially displaced atangles 0°/N, 150°/N, 270°/N, 60°/N relative to the teeth of a first oneof the sets of teeth.
 25. The stator device according to claim 23,wherein the stator device comprises four sets of teeth and axial widthsof the four sets of teeth are 1 unit, √3 units, √3 units, 1 unit,respectively.
 26. The stator device according to claim 16, wherein theelectric machine is a rotary machine, and wherein the moving device is arotor.
 27. The stator device according to claim 16, wherein the movingdevice is a mover arranged to move linearly in the direction of motionof the moving device.
 28. The stator device according to claim 27,wherein each stator core section is a soft magnetic structure.
 29. Thestator device according to claim 16, wherein the coil is arrangedbetween the first and the second stator core sections.
 30. The statordevice according to claim 16, wherein the stator device and the movingdevice constitute a modulated pole machine.
 31. The stator deviceaccording to claim 16, wherein the stator device and/or the movingdevice comprise a three-dimensional (3D) flux path including a flux pathcomponent in the transverse direction relative to the direction ofmovement.
 32. The stator device according to claim 16, wherein eachstator core section comprises a stator core back section that iscontinuous along the direction of motion of the moving device, and a setof teeth extending from the stator core back section.